The track-roller bearing of this invention comprises an outer member or outer race ring and an inner member, or inner race ring within the outer member, and a self-lubricating fabric liner secured or bonded to the outside surface of the inner member. With the liner so secured in the bearing, unexpected premature failures of the bearing are avoided, and the life of the bearing is prolonged and is predictable. The invention also includes a method of constructing such a bearing.
In the self-lubricated bearing art wherein the lubrication is provided by a lining between the movable parts of the bearing, an early patent in this art U.S. Pat. No. 2,350,398 on a rod end bearing filed Dec. 6, 1940 and issued June 6, 1944 had a flexible fabric liner secured to the inside of the outer or socket member providing a lubricated or lubricating surface in engagement with the ball within the socket. In the subsequent 40 years, many millions of self-lubricated bearings of different constructions have been manufactured using such a liner within the bearing, and although the rod end type of bearings represented a substantial part of that number, a liner for lubrication has also been incorporated in other types of bearings such as journal bearings, spherical bearings or self-aligning bearings, special bearings of various types, and track rollers. These are generally bearings for an installation where relative speed of movement between the two bearing parts is low and in the range of substantially zero to 20 surface feet per minute. Lined bearings of the type under consideration here eventually fail due to wear-out of the liner system and such wear-out is a function of the load times the differential in movement between the two bearing members. Thus, if a very heavy load were applied the speed of rotation must be very slow in order to obtain satisfactory life. Conversely, under light loads relatively higher speeds can be accommodated.
With the advent of polytetrafluoroethylene material sold under the trademark TEFLON, that material has been used in the fabric liner successfully, and has contributed to the wider use of self-lubricated bearings as described above. Also contributing to the broadening use of lined self-lubricating bearings is the fact that they will operate successfully in a wide temperature range, are resistant to different corrosive environments, and being self-lubricating, maintenance is reduced, and their life is superior in many installations relative to the life of a conventional anti-friction bearing for such an installation.
Over this long period of use of the self-lubricating bearing, the liner has been bonded to the inner surface of the outer race member of the bearing. The adhesive or bonding material is of a liquid or soft consistency when the liner is bonded to a bearing part surface, but it becomes hard when dried and the bearing is ready for and is put into commercial use. For some of the types of bearings the liner with such bonding has provided a satisfactory wearing condition and life. However, for a track roller with an unsupported rotating outer race ring and where the load accommodated by the bearing is applied on such outer race ring, it has been found that the continuous compression-relaxation cycling with every revolution of that outer race ring in the relative movement between the track and the bearing, the liner material itself adhering to such inner surface of such outer ring breaks up or disintegrates thereby ruining the liner. In fact, it appears that such continuous working of the fibers as they enter and exit from the load zone results in breakage of the individual fibers. The fabric breaks down and pulls apart, and the load then forces it to flow out of the bearing. The liner is thus destroyed and the bearing must be replaced. Because the self-lubricated track roller may be installed in a relatively inaccessibeleplace, and because the destruction of the liner and termination of bearing life is not readily predictable, it is necessary to either check on the condition more frequently than should be required or suffer the consequences of failure due to such destruction at a very inopportune time. Hence, the matter of checking on the bearing condition and life and the replacement of the bearing pose very serious and costly problems in the care of the equipment with which the bearing is installed. However, the practice of bonding such fabric liner to the inside surface of the outer race is universal in the structure used commercially in this field of bearings for all of the long period of use, and such practice continues. The resulting problem in self-lubricated lined track rollers so assembled has remained unsolved until the present invention.
In the bearing of the present invention, and in the method of constructing such bearing, the fabric liner is bonded to the outer surface of the inner ring, which remains stationary during bearing operation. The bonding agent hardens when it is completely dried, the inner ring remains stationary when pressure is applied during operation, the bond is maintained for the life of the bearing, and the fabric does not break down prematurely and pull apart. The life is uniformly predictable in such a track roller.
The extensive patent art on lined self-lubricating bearings confirms the consistent practice over the years in the patented bearings referred to above with respect to the method of manufacturing such bearings and the method of bonding the fabric liner to the inner surface of the outer race ring or other bearing part, except for the McCloskey U.S. Pat. No. 3,266,123 filed Apr. 7, 1965, and issued Aug. 16, 1966. This is on a self-aligning bearing assembled by deformation of the outer bearing member which is discussed in the Prior Art Statement filed herewith and points out that the liner is described as being optionally adhered to one of the members of the bearing as between the inner and outer members. In view of the long and consistent practice in the industry up to the present time of bonding the liner to the outer member, this optional very sparse description in 1966 showed a total lack of knowledge of the differences between bonding of the liner in these two different positions in that type of bearing, and very clearly failed to teach the art the advantage of bonding the liner to the inner member of a track roller as in the present invention.
The track roller of the present invention is a different type of bearing with different applications for the same than a self-aligning bearing. In the three examples described in the sentences beginning in column 2 line 51, and column 3 line 24 and line 34 of such McCloskey patent, the liner is specifically described by McCloskey as bonded to the outer member. In commercial practice, self-aligning bearings are manufactured by deforming the outer ring over the ball and when a self-lubricated liner is used, it is placed in the inside of the outer race ring for bonding thereto. When the outer race ring is deformed to enclose the ball, the adhesive on the liner is secured to the inside of the outer race ring just as McCloskey describes the liner in the outer race ring in columns 2 and 3 above. In a track roller the outer race ring must be hard and non-deformable in the manner of the self-aligned bearing, the inner race ring cylindrical, and the assembled bearing is not misalignable.
Contrary structurally to the McCloskey patented bearing; the inner and outer members of the present bearing invention are normally machined in their ultimate condition with a cylindrical raceway on the inside of the outer member, and an outer cylindrical surface for the inner bearing member. These bearing members do not lend themselves to deforming into a different configuration during manufacture as in McCloskey. The adhesive for the self-lubricating fabric liner is provided on only one side as contrasted to an optional placement on either side, and that adhesive is adhered to the outer surface of the inner member.
The track roller of the present invention and the self-aligning bearing of the McCloskey patent are thus very different structurally, and are used in very different applications such that one must describe them as being in different families, and of materially different types in the bearing field. This fact is further illustrated in that a self-aligning bearing must of a certainty be structured to accommodate a thrust load, while a track roller is not specifically designed for a thrust load because the installation thereof does not normally produce a thrust force.